Environmental concern of soil and groundwater contamination along with governmental mandated requirements to remedy this problem has prompted the need for rapid and cost effective subsurface characterization methods to determine chemical contaminants therein. Prior traditional subsurface soil characterization techniques include collection of field samples and subsequent analysis in the laboratory for both chemical and elemental analysis. The samples are initially collected from a bore hole, monitoring well or penetrometer sampler which in turn are taken to a lab for analysis using standard analytical procedures, atomic absorption or inductively coupled plasma emission processes for determining the types of contaminants and concentration thereof. These traditional techniques take relatively long time periods to perform as to sample extraction and preparation to laboratory analysis thereof, thus not suitable for examining large land areas where soil contamination has occurred. Additionally, these prior techniques are prone to error due to loss of soil sample contaminant material prior to laboratory analysis resulting in less accurate results. An example of this methodology includes U.S. Pat. No. 5,435,176 by Manchek, III entitled "Hazardous Waste Characterize and Remediation Method & System," that teaches in one embodiment of that invention of taking siphoned samples of downhole vapors as well as core samples for analysis. This system transports examined vapors through connecting tubing to the surface using a heated carrier gas or fluid. Once on the surface, the vapors are analyzed using field portable analytical laboratory equipment. Note that this system's sampling technique uses a rotary drilling device to obtain measurements from the soil whereas the instant invention uses a push penetrometer system for in situ down hole analysis. Other types of penetrometer vapor samplers trap down hole vapors in absorbent chemical traps within the probe that are later brought to the surface for analysis.
Another in situ methodology for determining soil contaminants includes Grey et al.'s U.S. Pat. No. 5,246,862 entitles "Method and Apparatus for In Situ Detection and Determination of Soil Contaminants." This method requires use of reagent carrying tape that captures contaminants between the outer wall of the penetrometer and the soil wall formed by the penetrometer. An optical fiber coupling device transmits the response of a calorimetric reaction on the tape surface to the surface for analysis. U.S. Pat. No. 5,445,795 by Lancaster entitled "Volatile Organic Compound Sensing Devices" teaches of a vaporchromic sensor within a penetrometer unit with associated optical fiber techniques for detection of volatile contaminant compounds in the ground water/soil.
Yet other in situ methodologies include optical fiber penetrometer systems for determining both elemental and molecular contaminants. These systems use real-time monitoring methods using either: i) a fluorescence spectroscopic based system; or ii) a laser-induced breakdown spectroscopic (LIBS) based systems where emission spectra of elemental contaminants are gathered. Both fluorescence and LIBS systems are effective techniques for determining different compositional materials by irradiating the soil sample at differing radiant intensities. A fluorescence based technique is primarily used for examination of molecular materials such as petroleum hydrocarbons since fluorescent activity occurs when excited. The LIBS technique is primarily used for determining elemental atomic contaminants such as metals by breaking down molecular bonds of soil materials and reducing molecules into component atomic species which are in a plasma state that in turn produce emission spectrum of the atomic species which are in a plasma state that in turn produce emission spectrum of the atomic species. The LIBS based system requires features not found in a fluorescence based system such as a more durable light focusing subsystem for transmitting and receiving light signals in such a system due to the high peak irradiance values used. In particular, dielectric breakdown of a soil contaminant material requires flux values approximately 3 to 4 orders of magnitude greater than those needed for a fluorescence based system. LIBS is not a soil contamination determination system for use in quantifying molecular species concentration since most molecular materials in the soil dissociates during plasma production. In system form, these two techniques use different light excitation sources and components for focusing the light due to the differing required power levels for determining particular materials.
Examples of Fluorescence based soil penetrometer systems include U.S. Pat. No. 5,435,176 as discussed above that has a further embodiment of an optical fiber sensing system. Additionally, U.S. Pat. No. 5,128,882 of Cooper et al. entitled "Device for Measuring Reflectance and Fluorescence on In Situ Soil" and U.S. Pat. No. 5,316,950 of Apitz et al. entitled "Method for Quantitative Calibration of In Situ Optical Chemical Measurements in Soils Using Soil Class and Characteristics". These two additional teachings use a penetrometer probe that use a light source or low powered laser source, e.g. a N.sub.2 laser. These optical light sources operate at low power levels around 10.sup.4 W/cm.sup.2 range or less. The observed optical data determines what types of molecular chemical contaminants are present in the soil, e.g. petroleum hydrocarbons using their fluorescent spectra when excited by an electromagnetic (EM) ultra-violet light source.
U.S. Pat. No. 5,379,103 by Zigler entitled "Method and Apparatus for In Situ Detection of Minute Amounts of Trace Elements" is an example of the LIBS system where a mobile laboratory issued for in situ detection of organic and heavy metal contaminants in ground water. This teaching requires a much higher powered laser source with higher irradiance values of around 10.sup.8 W/cm.sup.2 for proper excitation of metallic materials for determining their respective emission spectra.
The pnetrometer system of the instant invention collects real-time soil classification/layering data similarly to those methods used in U.S. Pat. No. 5,128,882 and 5,316,950 as discussed above. This methodology allows for down hole real-time analysis of liquid/vaporous samples for detection of contaminants in the soil.
The instant invention's geophysical sensing sampler module has a self-contained heating and aspirating sample chamber in the probe for enhancing real-time data collection and spectral analysis of liquid and/or gaseous samples at various down hole locations during a single penetrometer push operation. The real time collection of subsurface stratification data is needed for determining locations where subsurface contamination is suspected and where sample analysis is desirable. The conduct of real-time spectral analysis on down hole samples in the penetrometer sampler module's sampling chamber is faster than conventional sampling methods, less expensive, and does not bring contaminants to the surface that may result in equipment contamination and/or the generation of contaminated wastes. This results in more accurate data when compared to previous in situ methods that use either the fluorescence or Roman penetrometer as discussed above, since the analyte is more efficiently separated from the soil matrix by localized heating by the penetrometer's sampler module in proximity to the examined soil formation, resulting in tine efficient, more accurate sampling of the soil under examination.
Accordingly, the present invention is an improved over current in situ fluorescence based systems that examine soil samples through a down hole window in the probe. In particular, it is more reliable and time efficient since contaminant analytes are gathered in the down hole sampler module's sample chamber.